Recently a technique has been used for forming curved members with integral channels. Initially, the channels are created in one of two flat plates. The plates are then vacuum brazed together over their confronting surfaces to form a composite plate. The composite plate is then formed, such as by hydroforming, into a curved shape.
Although this technique works fairly well there are some distortions in the channels due to the bending and forming. The thought occurred to the present inventor that the plates could first be formed into complementing curved shapes and then brazed or otherwise joined together. The necessary channels are formed by machining grooves in one of the plates after shaping, but before joining. The common wisdom taught, however, that vacuum brazing of curved parts was not practical because uniform contact across the adjacent surfaces was not achievable. Even spring loading techniques, used in joining flat plates, do not work well with curved plates and are often less than satisfactory in joining flat plates.
Other techniques for joining curved members include dip brazing, but that technique is not practical when these members have long or tortuous flux paths. Further, residual flux salts trapped between the members can cause a severe corrosion problem. Such problems prohibit the use of dip brazing to form composites that are used in high reliability military and space applications.